Tweaking a Hollis H160

[boulderjohn]

I got a used Hollis H160 a while ago at a good price, so good that I did not do a lot of research on it. I am now trying to figure out how to make that "good deal" work out for me.

The problem I am trying to solve is one of buoyancy and trim. With no weights in it, it is still negative in fresh water. I would like it to be at least neutrally buoyant, if not a tiny bit positive in fresh water. With no weights in it, it is very nose light--it sinks to the bottom with the nose pointed up. If I put a single weight in, it is nose heavy, and it is, of course, even more negative than before.

I got a suggestion to glue strips of 7mm neoprene to the cowling.

Any other ideas?

 

[elan]

Lighter batteries ? If its not an option - run a hollow PVC pipe along the body?
Neoprene will be useless at depth.

 

[tstormdiver]

As I wrote you, John, I was never able to get past that problem on the H- 160 I had & Hollis did not seem to have a solution either. Part of the reason I went to the Cuda 650. Maybe try some pouches of weight further up in the nose, instead on top of the battery. You'll need to make sure you seal & secure them solidly. You may be able to get away with less weight & be able to balance it out. Unfortunately the battery is very heavy. Don't really have any other ideas,....

 

[PfcAJ]

You might be able to remove material from the inside of the scooter somehow. I had to do that with my older PVC Gavins. Hole-saw to the bulkheads. I don't know what's inside the Hollis, but take a look and see what's needed and what truly isn't. Remove the latter.

 

[boulderjohn]

You might be able to remove material from the inside of the scooter somehow. I had to do that with my older PVC Gavins. Hole-saw to the bulkheads. I don't know what's inside the Hollis, but take a look and see what's needed and what truly isn't. Remove the latter.

Scary words to a mechanical nitwit like me.

 

[tstormdiver]

You might be able to remove material from the inside of the scooter somehow. I had to do that with my older PVC Gavins. Hole-saw to the bulkheads. I don't know what's inside the Hollis, but take a look and see what's needed and what truly isn't. Remove the latter.

I don't know of anything off the top of my head that can be removed. Here's a picture of the H-160 without it's hull:


The battery is part of the rear end counter weight & helps to balance it out. The "stilts" hold the battery in place,.... kind of free floating inside, that is why the unit is so well balanced. The nose light,... might be able to be removed,.. but then you would have to find something to plug the hole & allow the hull to be screwed on (it does not have clamps like most DPV's),.. That is the only hull penetration & is held in place by a large C- ring clip. The rest of the hull is a solid, molded aluminum structure. In the rear, it is just the motor compartment, sealed off by a glass shield & not at all easy to get to.

 

[PfcAJ]

Looks like a rough situation. Maybe replace those stilts with something lighter? Are they solid or hollow?

Is the whole thing just a little negative or is it very negative? What does Hollis say about this?

 

[tstormdiver]

The stilts are solid aluminum alloy (I think). When I had my H-160, it is pretty negative. It doesn't crash to the bottom when dropped in, but it doesn't waste any time getting down there either. At my local quarry, an OW class manged to kick it off a ledge, over a wall into 90 ft of water. Had to go looking for it in very cold water (I wasn't too happy about that). Once in motion though, it is so well balanced, that it "planes" out neutral, for lack of better description,... but once stopped, it begins to drop. The tail section is VERY negative, the integrated weights that are screwed onto the battery, along with the weight of the battery balance it out. Without both or one of the weights, it wants to go pretty much, straight nose up.

The plus side to that DPV, is that it is so well balanced that the manouverablility is incredible. It turns nearly as sharp as an Oceanic Mako. I had very little wrist fatigue on it & I have tiny wrists.

With my Cuda 650, it took me nearly an entire day to do it,.... but I was able to get that thing so well weighted that it floats level about 2" off the bottom & the handle is at the 2 o'clock position when near it's fullest speed (perfect for me).

Here is a thread I started in Hollis' forum & their reply: http://www.scubaboard.com/forums/hollis/374285-changes-h-160-dpv-weighting.html

 

[PfcAJ]

Negative scooters suck, especially in caves and if you have to tow it. It becomes a real issue then.

I would try and remove one of those stilts and replace it with a PVC pipe. That might give you enough positive buoyancy to figure a way to trim it flat.

 

[boulderjohn]

Negative scooters suck, especially in caves and if you have to tow it. It becomes a real issue then.

That is what prompted this thread. I had it in Jackson Blue with the flow absolutely ripping. Pulling line out of the cavern zone without dragging the scooter required some real artistry, artistry that I have not mastered. My instructor felt that slightly negative but nose light was preferable to very negative and trimmed, and I believe he was right.